1. Field of the Invention
The present invention relates to a deflection apparatus for cathode ray tube of a display, and more particularly it relates to a deflection apparatus for cathode ray tube which shows deflection distortion.
2. Description of the Prior Art
A deflection apparatus for cathode ray tube comprises fundamentally of vertical scanning coils and horizontal scanning coils. There are three basic types of deflection apparatus for cathode ray tube well known in the prior art, which are classified as follows:
(1) A saddle type, in which windings on bobbin are made to form saddle-shaped coils and arranged on the inner surface of the deflection yoke itself.
(2) A semi-toroidal type, in which horizontal scanning coils are prepared in the same manner as the above saddle type, and vertical scanning coils are directly formed toroidally on the surface of the deflection yoke itself.
(3) A slot type, which is one variation of the aforesaid saddle type, in which plural grooves are formed in the radial direction in the deflection yoke and windings are mounted therein.
Among these three, the semi-toroidal type of (2) is the mainstream of the applied for deflection yokes because they result in high efficiency and low resistance for direct current.
An example of the semi-toroidal deflection apparatus in the prior art will now be described with reference to the accompanying drawings of FIG. 1 and FIG. 2. Referring to the drawings, a trumpet-shaped deflection yoke (1) is made of a ferrite core and vertical scanning windings (2) are wound thereabout to form a toroid. A trumpet-shaped insulator (3) is arranged on the inner surface of the deflection yoke (1) and saddle type horizontal scanning coils are arranged thereon. The insulator (3) holds the horizontal scanning coils and at the same time, it holds the deflection yoke too.
As is illustrated in FIG. 1 and FIG. 2, a magnetic field is vertically generated by the horizontal scanning coils and forms a loop of magnetic field through the deflection yoke (1). However, as the vertical scanning windings (17) are arranged in the horizontal magnetic field, eddy-current by the horizontal field is induced on the surface of the vertical windings and causes heat generating problems. In the recent high resolution cathode ray tubes, as they employ a higher frequency to drive horizontal scanning coils at for example 64-120 kHz, the tendency to generate heat is increased. Not only for the semi-toroidal type, two deflection windings generally have an induction heating problem when one of the deflection winding is heated by the magnetic field generated by the other windings.
One or both horizontal scanning coils and vertical scanning coils, or a deflection apparatus for cathode ray tube, which are assembled from these coils on trumpet-shaped ferrite core, are generally supported on a plastic resin frame. Heretofore, it was necessary to employ an expensive heat-resistant plastic material when temperature of the material might rise to or above about 90.degree. C.